The Nainital-Cape Survey

for pulsating Chemically Peculiar stars





The Nainital-Cape Survey is a collaborative survey program initiated in 1997 between the Aryabhatta Research Institute of Observational Sciences (ARIES - formerly State Observatory), Manora Peak, Nainital, India and the South African Astronomical Observatory (SAAO), Cape Town, South Africa. The main onjective of this joint venture is to search for the pulsational variability in chemically peculiar stars in Northern and Southhern hemisphere.

The amplitudes of the light variations in these stars are so minute (<1%) that an excellent photometric site and highly sensitive and stable instrumentation are required to observe them. With care, such precision can be routinely attained at a good photometric site such as ARIES or SAAO.

These stars are designated 'CP' (for 'chemically peculiar') because their spectra exhibit abundance anomalies that manifest as extreme over- or under-abundances of various chemical elements. The spectral anomalies are caused by radiative diffusion in these stars, which pushes certain elements to the surface of the star (hence causing those elements to appear to be over-abundant) and gravitational settling of other elements in the atmosphere (hence causing those elements to appear to be under-abundant).

The Nainital-Cape survey is one of the largest ground based legacy survey ever conducted using one meter class telescopes at ARIES and SAAO where more than 350 stars were monitored to study the internal structure of chemically peculiar stars in the presence of surface inhomogeneity, magnetic field and stellar activities such as rotation, pulsation. The interesting candidates are now being investigated using the highly precise photometry from space missions such as K2, TESS. The high-resolution spectroscopy is being performed from state-of-art instruments such as HERMES and HESP.